A color image can be synthesized by combining discrete primary color images (e.g., red, green and blue). In display systems using liquid crystal display panels, each primary color image can be generated by a respective display panel. The primary color images are then combined by an optical combiner to form a synthesized color image.
To synthesize an accurate color image, the display panels must be precisely aligned with respect to each other. The display panels must also be precisely aligned with the optical axis of the optical combiner. These alignments cannot be predetermined because there is a large tolerance in the optical properties of individual display panels.
In typical projection display systems using display panels, the display panels are fixed to a supporting structure of the display system. The beam combiner is then inserted in the optical path of the display panels. Such systems cannot be aligned until the display panels and beam combiner are fixed to the display system. Such systems contain many mechanical parts to facilitate image alignment between the optical combiner and the display panels. Assembly workers must have adequate skills to achieve the alignment after assembling the display system.
In projection display systems, the display panels are subjected to thermal stress, which can misalign the display panels. A spatial misalignment of the display panels relative to each other or to the optical axis of the optical combiner can degrade the synthesized image.